1. Field of Invention
The present invention relates to a process for preparing reaction injection moldings containing polyurea materials. More specifically the present reaction relates to the use of specified isocyanate reactive materials in the preparation of the reaction injection moldings.
2. Brief Description of the Prior Art
Reaction injection molded (RIM) materials are well known in the art and have met with substantial commercial success. U.S. Pat. No. 4,218,543 describes the use of relatively high molecular weight hydroxyl group containing materials, aromatic diamines as chain extenders, and isocyanates for the production of RIM parts.
More recently, the activity in the art has been towards the production of polyurea RIM parts. Typically, these parts are made from relatively high molecular weight polyethers which contain amine groups, diamine chain extenders, and isocyanates. Typical of the materials used and the technologies known in the art are those described in U.S. Pat. Nos. 4,396,729, 4,433,067, 4,444,910, 4,530,941, 4,774,263 and 4,774,264. As is known in the art, RIM parts are generally produced from two separate streams. One stream generally contains the isocyanate component, while the other stream contains the amine-containing polyether and the amine chain extender. Amine-containing polyethers (prepared by hydrolysis of isocyanate prepolymers) where the amine groups are attached to aromatic groups are generally too viscous for use in conventional RIM machinery, while amine-containing polyethers where the amine groups are attached to aliphatic moieties are too reactive to be used alone with conventional aromatic isocyanates.
Recently, the use of aminocrotonates in reaction injection molding applications has been discovered. See U.S. patent application Ser. No. 523,769, filed on May 15, 1990. In addition, U.S. patent application Ser. No. 524,268, filed on May 15, 1990, relates to production techniques for similar compounds which can contain aliphatic as well as aromatic bound amine groups. Similar compounds and their methods of production can be found in U.S. Pat. Nos. 3,666,726 and 3,691,112.
From the foregoing, it is clear that there is a continuing need for a suitable combination of polyamine and polyisocyanates which would constitute a RIM composition and process for preparing RIMs which has the desired processing and performance properties. The present invention provides such a process.